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参数资料
| 型号： | LTC1878EMS8#TR |
| 厂商： | Linear Technology |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 8MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 6 V |
| 输入电压： | 2.65 V ~ 6 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 550kHz |
| 电流 - 输出： | 600mA |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-MSOP |
| 其它名称： | LTC1878EMS8TR |
LTC1878
APPLICATIO S I FOR ATIO
Thermal Considerations
In most applications the LTC1878 does not dissipate
much heat due to its high efficiency. But, in applications
where the LTC1878 is running at high ambient tempera-
ture with low supply voltage and high duty cycles, such
as in dropout, the heat dissipated may exceed the maxi-
mum junction temperature of the part. If the junction
temperature reaches approximately 150 ° C, both power
switches will be turned off and the SW node will become
high impedance.
To avoid the LTC1878 from exceeding the maximum
junction temperature, the user will need to do some
thermal analysis. The goal of the thermal analysis is to
determine whether the power dissipated exceeds the
maximum junction temperature of the part. The tempera-
ture rise is given by:
T R = (P D )( θ JA )
where P D is the power dissipated by the regulator and q JA
is the thermal resistance from the junction of the die to the
ambient temperature.
The junction temperature, T J , is given by:
T J = T A + T R
where T A is the ambient temperature.
As an example, consider the LTC1878 in dropout at an
input voltage of 3V, a load current of 500mA, and an
ambient temperature of 70 ° C. From the typical perfor-
mance graph of switch resistance, the R DS(ON) of the
C C2
LTC1878
P-channel switch at 70 ° C is approximately 0.7 ? . There-
fore, power dissipated by the part is:
P D = I LOAD2 ? R DS(ON) = 0.175W
For the MSOP package, the θ JA is 150 ° C/ W. Thus, the
junction temperature of the regulator is:
T J = 70 ° C + (0.175)(150) = 96 ° C
which is below the maximum junction temperature of
125 ° C.
Note that at higher supply voltages, the junction tempera-
ture is lower due to reduced switch resistance (R DS(ON) ).
Checking Transient Response
The regulator loop response can be checked by looking at
the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, V OUT immediately shifts by an amount
equal to ( ? I LOAD ? ESR), where ESR is the effective series
resistance of C OUT . ? I LOAD also begins to charge or
discharge C OUT , which generates a feedback error signal.
The regulator loop then acts to return V OUT to its steady-
state value. During this recovery time V OUT can be moni-
tored for overshoot or ringing that would indicate a stabil-
ity problem. The internal compensation provides adequate
compensation for most applications. But if additional
compensation is required, the I TH pin can be used for
external compensation using R C , C C1 as shown in
Figure 7. (The 220pF capacitor, C C2 , is typically needed for
noise decoupling.)
OPTIONAL
R C
C C1
1
2
RUN
I TH
PLL LPF
SYNC/MODE
8
7
BOLD LINES INDICATE
R1
R2
3
4
V FB
GND
V IN
SW
6
5
L1
HIGH CURRENT PATHS
+
+
C IN
+
C OUT
V OUT
V IN
–
–
1878 F07
Figure 7. LTC1878 Layout Diagram
12
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相关代理商/技术参数 |
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| LTC1878EMS8TRPBF | 制造商:Linear Technology 功能描述: |
| LTC1879EGN | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1879EGN#PBF | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LTC1879EGN#TR | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1879EGN#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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